The video conferencing system allows compressed digital video signals to be interchanged between all four major NRAO sites (AOC, Charlottesville, Green Bank, and Tucson) over our frame-relay Intranet. The equipment that enables this capability at each site is:

• A "Polycom ViewStation" with a video camera, two microphone pods, and a self-contained video signal processor,
• A remote control unit for the ViewStation, allowing control of each system by a participant at the conference table,
• A Document Camera for showing high-quality video images of papers, transparencies, and hardware with a wide range of magnifications, and
• A secondary video camera with its own remote control,
• Two large TV monitors.

This basic equipment allows high-quality "point-to-point" video conferencing between any two NRAO sites. An additional "Hub" (Radvision Multi-Conferencing Unit) located in Charlottesville permits:

• three or four-way conferencing within the NRAO, and
• conferencing with non-NRAO sites via an ISDN Gateway.

The ISDN Gateway is connected directly to the Charlottesville Phone PBX. It can be used to link one or more NRAO sites with external sites that have ISDN video conferencing capability. (It has been used for video conferences with European and Japanese sites, for example.)

Compressed digital video transmission over our Intranet provides a picture quality similar to that of videotape, with a small time delay between an event at the remote site and the signal seen on your TV monitor. The delay is more noticeable in multi-site calls than in point-to-point calls, and conference participants need to be somewhat aware of it, e.g. when attempting to interrupt a speaker at another site.

During a multi-site conference, the incoming video signal seen at each site is currently that from the site sending the strongest audio ..."voice-activated video switching." RadVision will soon offer a continuous-presence feature that will display video from all four sites at once in a "Hollywood Squares" arrangement.

A PC was purchased with each site's video conferencing system to allow:

• computer-based presentations (via Netscape, Powerpoint or other software) at each site, and
• high-quality sharing of such presentations between computers at each site in parallel with the video signals during meetings or seminars.

Each NRAO site also has a high resolution LCD projector which may also be connected to its video conferencing PC for computer presentations, or directly to the Polycom ViewStation to show video signals in larger format.

Digital whiteboards have yet to be purchased; their acquisition and deployment is on hold pending evaluation of our use of the PC and screen sharing capabilities between sites.

Components of the basic Polycom system